Method of spinning polyvinyl alcohol fibers



June 151953 TsuKumb TOMONARI ETAL METHOD OF SPINNING POLYVINYL ALCOHOL FIBERS Filed'Apr il 8, 1950 MM; 73u/ru/wo Ema/ma:- MIcH/JH20 A3050:

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AGENT Patented June 16, 1953 METHOD OF SPINNING-POLYVINYL ALCOHOL FIBERS Tsukumo Tomonari, Osaka, and Michijiro Akaboshi, Kurashiki, Japan, assignors of onefcurth to Omni Products Corporation, New York, N. Y., a corporation of New York Application April. 8, 1950, Serial No. 154,872 In Japan July 26, 1949 1.01am. (CI. 18-54) polyvinyl alcohol fibers where the coagulating rate is slow, it is necessary to make the clipping length as long as 500 mm.-l,000 mm. at spinning speeds of about-50 meters per minute. If it is desired to increase the spinning speed (for example, it is possible to uses. speed of 90 meters per minute in the viscose method), a longer dipping length is required. For spinning methods where the filaments have to travel through considerable lengths of the coagulating bath, it has been proposedto let the spinning solutions flow upwardly together with the coagulating medium in order to save floor space. Thismethod should be of particular advantage for spinning polyvinyl alcohol and similar filaments where the specific gravity of the spinning solution is considerably'lower than the specific gravity of the coagulating bath. This difference in the specific gravities causes the spinning solution to float upwardly in the rising column of the coagulating liquid, and the filaments which are being formedin the coagulating bath are subject to a gentle stretching, which should prevent breakages.

However, when it. was attempted to prepare polyvinyl alcohol filaments by the up-spinnin process, it was found that the conventional devices were not suitable and that the filaments broke, especially in the zone where the coagulation of the filaments started. Breakages of the filaments became particularly frequent when the same apparatus had to be used under changing conditions of concentration, spinning speed, temperature, etc.

It is a principal object of the invention to provide a method for up-spinning polyvinyl alcohol and similar filaments with a minimum of breakages.

Another object of the invention is to provide an apparatus suitable for carrying out said method.

The present invention provides an improved method and apparatus for producing filaments from polyvinyl alcohol, which method reduces to a minimum the occurrence of breakages by allowing the filaments to take form in an upwardly flowing unturbulent column of the coagulating medium and by applying stretch to the filaments only after they have sufficiently solidified.

An apparatus suitable to carry out the method of the invention consists essentially of areaction chamber in which the spinning solution is brought in contact without turbulence with the coagulating liquid, and of vertical or inclined tubes of much smaller diameter through which the coagulating liquid and the spinning solution pass upwardly for a length of travel sufficient to solidify and stretch the coagulated filaments.

When the rising coagulating liquid enters the narrow tube, the rate of travel of the liquid is increased corresponding to the reduction of the diameter of the rising column, and this increased rate of travel exerts a stretching action on the filaments which are being formed. These filaments will break if they are subjected to a stretching action or to any stress by turbulence before they are sufiiciently solidified.

Our invention is illustrated in the accompanying drawings, in which:

Figure 1 is an elevation of the spinning machine embodying the present invention, and

Figure 2 is a sectional elevation showing the essential part of the spinning machine.

Referring now to the drawing,- I designates a vertical pipe having an inner pipe 2 fixed therein, through which the coagulating bath and the spinning solution are forced upwardly. 3 represents an over-flow tank, through the bottom of which the upper end of the inner'pipe 2 is extended. 4 represents the reaction chamber having fitted to its bottom a spinneret 5 which is connected to the filter 6. The chamber 4 is provided with openings which are normally closed by the cover I. 8 designates a pump such as a gear pump driven by a suitable motor (not shown). Around the spinneret 5, there is arranged a ring-shaped pipe 9 having a. number of small nozzles, which is connected to the source of the coagulating hath (not shown) through the pipe l0 and the regulating valve II. The over-flow tank 3 is provided with an outlet pipe [2 which delivers the excess coagulating bath to a receiver l3, thence the bath is returned to the collecting tank M. I 5 represents godet rollers for transmitting the spun fibers to following machines (not shown).

As shown in Fig. 2, the lower end I6 of the pipe 2 is preferably flared out and the space between the pipes l and 2 is used as a heating jacket or a heat insulating chamber.

The operation of the present spinning machine shown in the drawing is explained in the following:

The coagulating liquid is fed from the pipe slowly and uniformly through the nozzles of the annular pipe 9 into the chamber 4 wherein it flows upwardly without turbulence until it enters the funnel-shaped opening l6. Then it flows upwardly at an increased speed through the narrow tube 2; the liquid overflowing at the upper end of said tube into the tank 3 is recycled through the pipe l2 and the funnel l3 in a reservoir for repeated use.

A certain definite amount of the spinning solution is pumped up by the gear pump 8, through the filter 6, and spinneret 5 into the coagulating bath without turbulence. The spinning solution begins to coagulate and is assembled into the funnel opening [6 together with the coagulating bath. While it fiows up through the coagulating tube 2, it completes the coagulation and is transformed into filaments I! which pass to the following processing stages over the godet roller 15.

The upwardly flowing column of coagulating liquid and spinning solution comprises two sections sharply distinguished by their physical conditions. The lower section is a relatively wide column of undisturbed flow where the spinning solution starts coagulating to filaments. The rate of coagulation depends on the concentrations and compositions of the components, on the polymerization degree of the filament forming material, temperature, etc. If the filaments formed in this section have not sufficiently solidified, they will be broken when entering the pipe 2, i. e., the second section.

In this second section, the rate of upward travel of the column is considerably increased because of the sudden reduction of the diameter of the column, and the filaments are stretched. As stated hereinbefore, the filaments must have a certain strength when entering the pipe 2 to avoid breakages. On the other hand, if the solidification of the filaments has advanced too far, the stretch exerted during the travel through tube 2 will not be sufiicient to produce the desired elongation. The jacket formed by the tube I around tube 2 allows of passing a heating or cooling medium therethrough; in this way, the temperature of the liquid column in tube 2 may be controlled so as to obtain the desired rate of coagulation and solidification of the filaments therein.

Depending upon the density and qualityv of the spinning solution, its separation from the spinneret 5 may be sometimes difficult. In such a case, the supply of the liquid may be stopped by closing the cock H and by opening the window or cover 7 located at a point about mm. above the spinneret, and the free flow of the spinning solution is restored by suitable manipulations. Then the cover I is closed and the cock II is opened again to feed the coagulating solution. The spinning solution floats on the coagulating solution and fiows upwardly therewith, and the filaments are collected at the top of the pipe 2 and then wound up by the godet roller I5.

It will be understood that while a particular embodiment of the invention has been described, the invention is capable of further modification, and the present application is intended to cover such changes or modifications as within the spirit of the invention or scope of the following claim.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent of the United States is:

A method of spinning polyvinyl alcohol fibers comprising the steps of extruding a polyvinyl alcohol solution into an up-flowing column of a coagulating liquid having a higher specific gravity than said polyvinyl alcohol solution, imparting to said coagulating column and said polyvinyl alcohol solution a parallel upward direction of flow without turbulence, maintaining said unturbulent parallel fiow until the polyvinyl alcohol coagulates to filaments, subsequently reducing the diameter of said column, thereby increasing the rate of flow thereof, and stretching said coagulated filaments by said increased rate of flow and the uplift of the filaments in the specifically heavier column of the coagulating liquid.

TSUKUMO TOMONARI. MICHIJIRO AKABOSHI.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 827,434 Friedrich July 31, 1906 838,758 'I'hiele Dec. 18, 1906 2,138,394 Wuppermann Nov. 29, 1938 2,239,718 Izard Apr. 29, 1941 2,288,982 Waterman et a1. July 7, 1942 2,453,839 Furness Nov. 16, 1948 FOREIGN PATENTS Number Country Date 415,323 Great Britain Aug. 23, 1934 

